Pushing the limits of existing plasma focus towards 10¹⁶ fusion neutrons with Q = 0.01

Abstract

Existing conventional megajoule plasma focus machines with 2–3 MA are producing fusion neutron yields of several times 1011 in deuterium operation, the fusion yields being predominantly beam-gas target. Increasing the current to 10 MA and using 50%-50% D-T mixture would scale the neutron yield towards 1016 D-T fusion neutrons. In this work, we derive the Lawson criterion for plasma focus devices with beam-target fusion neutron mechanism, so that we may glimpse what future technological advancements are needed for a breakeven Q=1 plasma focus. We do numerical experiments with a present-day feasible 0.9 MV, 8.1 MJ, 11 MA machine operating in 100 Torr in 50%-50% D-T mixture. The Lee Code simulation gives a detailed description of the plasma focus dynamics through each phase, and provides plasma and yield parameters which show that out of 1.1 × 1019 fast beam ions produced in the plasma focus pinch, only 1.24 × 1014 ions take part in beam-target fusion reactions within the pinch, producing the same number of D-T neutrons. The remnant beam ions, numbering practically 1019, exit the focus pinch at 1.9 MeV, which is far above the 115 keV ion energy necessary for optimum beam-target cross-section. It is proposed to regain the lost fusion rates, by using a high-pressure D-T filled, drift-tube to attenuate the energy of the remnant beam ions until they reach the energy for optimum fusion cross-section. Such a fusion enhancement tube would further harvest beam-target fusion reactions by increasing the interaction path length (1 m) at increased interaction density (6 atm). A gain factor of 300 is conservatively estimated, with final yield of 3.7 × 1016 D-T neutrons carrying kinetic energy (KE) of 83.6 kJ, demonstrating Q = 0.01.

Thermonuclearizing the plasma focus—converting plasma focus fusion mechanism from beam-gas target to thermonuclear

“…Increasing the taper ratio to 50 (for example, taper from 20 cm radius down to 4 mm) numerical simulation shows a pinch temperature of 200 keV in a pinch with radius 0.7 mm and length of 5 mm. Using a mixture of hydrogen and boron, aneutronic fusion may be expected using this tapered anode [25][26][27]. The ability to control temperature and volume are exceptional features of this method.…”